Method of preparing pelletized pesticidal compositions



Unite States Patent Office 3,056,723 Patented Oct. 2, 1962 1 3,056,723METHOD OF PREPARHNG PELLETIZED lPEdTICiDAL CQ MPQSITIQNS Arthnr L.Galloway, Mentor, @ltio, assignor to Diamond Aikali Company, Cleveland,Uhio, a corporation of Deiaware No Drawing. Filed Nov. 21, 196i), Ser.No. 70,448 7 Claims. (Cl. 16742) This invention relates to methods forpreparing biologically active compositions of matter and in particularto methods for preparing compositions for use in killing or preventingundesirable pests.

This application is a continuation-in-part of my copendihg application,Serial No. 779,530, filed December 11, 1958, now abandoned.

,It is to be understood, that as used hereinafter, the term pesticide orpesticidal composition is meant to refer to those toxicant compositionswhich are effective in killing or controlling the growth of plants,insects, microorganisms, fungi, bacteria and the like, and it isintended to refer broadly to those compositions commonly known asinsecticides, bactericides, fungicides, nematocides, herbicides and thelike.

Various types of pesticides have been proposed and are currently in use.These materials are characterized by their ability to attack orexterminate certain undesirable species of pests, their action beingselective in that desirable species are left substantially unaffectedand in a more or less healthy or vigorous state. The pesticidalcompositions which have been used include both inorganic and organicchemicals or compositions, some of the more common materials being thefollowing:

DDT (2,2-bis(p-chlorophenyl)-1,1,l-trichloroethane) 2,4-D(2,4-dichlorophenoxyacetic acid) 2,4-D (isopropyl ester) 2,4,5-T(2,4,S-trichlorophenoxyacetic acid) Dieldrin (1,2,3,4,10,10hexachloro-exo-6,7-epoxy-1,4,4a,

5,6,7,8,8a octahydro 1,4 endo,exo 4,8-dimethanonaphthalene) Sesone(sodium 2,4-dichlorophenoxyethyl sulphate) Endrin(1,2,3,4,10,10-hexachloro-exo-G,7-epoxy-1,4,4a,5,

6,7,8,8a octahydro-1,4,5,8endo,endo-dimethano-naphthalene) Heptachlor(l,4,5,6,7,8,8 heptach1oro-3a,4,7,7atetrahydro-4,7-endomethanoindene)Malathion (S (1,2 dicarbethoxyethyl) 0,0 dimethyl phosphorodithioate)Parathion (0,0-diethyl O-p-nitrophenyl phosphorothioate) DDVP (dimethyldichlorovinyl phosphate) OveX or Ovotran (p-chlorophenylp-chlorobenzenesulphonate) Lindane gamma-l ,2, 3 ,4,5,fi-hexachlorocyclohexane) Natrin (sodium 2,4,S-trichlorophenoxyethylsulphate) 3,4-dichlorotetrahydrothiophene 1,1-dioxide3,3,4,4-tetrachlorotetrahydrothiophene 1,1-dioxideDimethyl-2,3,5,6-tetrachloroterephthalate One method of applyingpesticidal agents of the type described above involves dissolving theagent in an appropriate solvent, with or without a surfactant, such as,water, kerosene, fuel oil, toluene, xylenes, etc., and applying theresulting solution, usually in the form of a spray, to the area desiredto be treated. Alternatively, the pesticidal agent may be dry mixed witha pulverulent diluent, such as, talc, finely-divided diatomaceous earth,ground pumice, Fullers earth, whiting, etc., and the resulting activedust applied to the areas to be treated. While these methods aresuitable for application at close range and where there is no danger ofcontamination of adjacent areas in which certain vegetation, insects,microorganisms or the like might be damaged, there has always been adistinct hazard in that particles of active spray or dust may be carriedover on to adjacent areas with harmful effects due either to the methodof application or to the fact that the particles of active agent aremiscarried by Wind or air currents. Additionally, sprays or dusts cannotbe applied to areas lying under heavy foliage, as the fine particles ofthe spray or dust will not penetrate the foliage. Progress in theapplication of pesticidal agents by aircraft has been retarded becauseof the above-mentioned difficulties.

Attempts have been made to solve these problems by incorporating thepesticidal agents into or upon pellets consisting essentially of fullersearth, natural clays, such as, attaclay, pumice, calcined diatomaceousearth, or other pelletized powders. While such pellets lend themselvesto control distribution by aircraft over a designated area, they leavemuch to be desired in that the bonding agents employed during thepelletizing operations are usually water soluble. The pellets are,therefore, adversely affected by rainfall or conditions of high humiditywhich cause slacking and progressive disintegration of the pellets.During periods of reduced humidity 01' drought, the resultingdisintegrating pelletsform dust which may be picked up by prevealingwinds, thereby causing damage to adjacent areas where the presence ofsuch agents would be undesirable. Furthermore, the disintegration ofsuch pellets accelerates the release of the pesticidal agents and theeffective life or period activity of the pelletized composition isthereby substantially reduced.

Additionally, in the preparation of such pelletized pesticidalcompositions, the pesticides are dissolved in a solvent and the solventsolution used to contact the pellets, the solvent being evaporated so asto deposit the pesticide on or inthe pellets. The solvents are generallyexpensive and toxic both to humans and to plants, and it is additionallyvery difficult to recover the solvents when they are evaporated.Similarly, problems of storing large quantities of solvent for use aswell as the flammability of most of these solvents, are alsoencountered. Where cheaper solvents, such as, water, are used, they arevolatilized only with difiiculty and hence are often left in thepellets. Moreover, during the solvent impregnation of pesticides on apreformed granule, fines are produced, which, although recoverable,cannot be used in preparing subsequent batches of granules and hence arenot readily usable. Problems are also encountered in using pesticides,such as, the above-mentioned Heptachlor, Endrin and Dieldrin, in thatthey are sensitive to the material of which granules have heretoforebeen formed and, hence, the granules must be deactivated before beingimpregnated with the pesticide.

It has also been found that the physical characteristics of thepresently-produced pellets cannot be materially altered so that theporosity, hardness and so forth of the pellets will pe controlled by thematerial of which it is made. This presents problems, in that, fordifferent types of applications, it is desired to change the porosity orhardness of the pelletized pesticide. To do this, at present, it isnecessary to alter the composition of the pellet in which the pesticideis impregnated by using a different material for the pellet. Finally, ithas been found that many of the pesticides in use today are onlyslightly soluble in the common solvents or are soluble only in waterand, hence, do not lend themselves readily for granule preparation.

It is, therefore, an object of the present invention to provide a methodfor preparing a novel, effective, biologically active material inpelletized form Without the use of solvents.

Another object of the present invention is to provide a method forpreparing novel, effective, biologically active agents, and inparticular pesticidal agents, having improved properties with respect tolength of active service, resistance to disintegration due to climaticconditions and resistance to deformation and disintegration duringapplication.

A further object of the present invention is to provide a method forpreparing such compositions which is easily carried out and readilyadaptable for use with a wide variety of biologically active materials.

Another object of the present invention is to provide such a methodwherein the physical properties of the pellets, such as, hardness andporosity, can be easily varied without the necessity of changing thebasic material of which the pellet is formed.

These and other objects will become apparent to those skilled in the artfrom the description of the invention which follows.

The method of the present invention envisions forming a mixturecontaining a dehydrated calcium sulphate, i.e., the anhydrous or thehemi-hydrate form, a biologically active substance, such as, apesticidal agent, which may be in the form of a wettable powder or adust concentrate. To this mixture is added only sufiicient Water to formthe dihydrate of calcium sulphate and effect the formation of pelletscontaining the biologically active material incorporated therein.Additionaly, the present method envisions that a portion of thedehydrated calcium sulphate can be replaced with a common clay, such as,attaclay, or a dispersing and/or a swelling agent, such as, sodium'bentonite, wheat flour, wood flour, or the like, thus giving apolletized composition having a variety of hardnesses and porosities. Bythis method of forming the granular material, it is not necessary tomake a solvent solution of the pesticidal agent, and hence evaporationof this solvent is not necessary and the problems encountered in the useof such solvents are prevented. Along this same line, it is found thatby the present method, pesticides which are insoluble or only veryslightly soluble in water or other solvents are easily formed intogranules where heretofore with these materials it has been necessary tomake a slurry of the material in order to form granules having thedesired pesticide concentration. It has also been found that thedehydrated calcium sulphate of the present granules, does not have to bedeactivated prior to being incorporated with some of the more sensitivepesticides, such as, Dieldrin, Endrin and Heptachlor.

Exemplary of the dehydrated calcium sulphate which may be used in thepresent method are those materials, such as, dental plaster, which arecommonly referred to as plaster of Paris. erence will be madehereinafter to plaster of Paris as being the preferred dehydratedcalcium sulphate. This, however, is not to be taken as limiting thepresent invention.

In forming the granular pesticidal composition by the method of thepresent invention, 25 to 90 parts by weight of plaster of Paris aremixed with 2 to 40 parts by weight of a 50% concentration dustconcentrate or wettable powder of the pesticide. Additionally, to 60parts by weight of a clay, such as, attaclay or kaolin, may also beadded. If desired, all or a portion of the clay may be replaced with adispersing or swelling agent, such as, bentonite, Wheat flour or woodflour, so as to cause a more rapid disintegration of the granules whenthey have been applied to the soil. To this dry mixture is added onlysufficient Water to form the dihydrate of calcium sulphate and toprovide the excess necessary to effect the formation of pellets. Themixture is stirred constantly during the addition of the water untilpelletizing of the mixture is produced. The moist mixture is then driedand screened to obtain granules of a size of between and 80 mesh, i.e.,granules which will pass through a screen having 10 openings per linearinch but will be retained on a screen having 80 openings per linearinch. Generally, granules which will pass through a screen havingAccordingly, for convenience, ref- 20 openings per linear inch and beretained on a screen having 40 openings per linear inch or which willpass through a screen having 30 openings per linear inch and be retainedon a screen having 60 openings per linear inch are preferred forcommercial application.

The amount of water added is found to be quite critical in that theremust be sufficient water to form the calcium sulphate dihydrate andprovide the excess necessary to efiect the pelletizing of the mixture.However, in no event, should the amount of water added be suificient toform a slurry or suspension of the dry materials. If this is done, alarge solid mass of plaster of Paris will eventually be formed, whichmass is not suitable for application without subjecting it to variouscrushing and grinding operations in order to obtain a material of ausable particle size. Not only is the use of large amounts of waterundesirable from the standpoint of the additional grinding and crushingoperations necessary to obtain a suitable product, but, additionally,the large excess of Water pres ent in the composition must be removedthereby further increasing the production cost. Moreover, when thepesticidal material is quite soluble in water, in evaporating this largeexcess of water, the pesticide effloresces to the surface of the mass ofplaster of Paris where it tends to shatter off thereby making itimpossible to produce granules having a uniform pesticide concentration.It is for these reasons that it has been found necessary to use onlysufiicient water to form the calcium sulphate dihydrate and provide onlyenough excess to eflect pelletizing of the composition. The pesticidalgranules are, thus, easily formed with only a minimum amount of crushingand drying required so as to provide granules of a uniform compositionat a considerable reduction in manufacturing cost.

It is believed that those skilled in the art can readily ascertain theamount of water required in each instance. This amount of water will, ofcourse, depend on both the amount of plaster of Paris present in themixture as well as the total amount of all of the dry substituents.Generally, it has been found that an amount of water which is about 2-6times the amount required to form the calcium sulphate dihydrate will besufficient to effect the required pelletizing of the composition Withoutforming a slurry or suspension of the material.

The present method may be conveniently carried out in equipment similarto that which is commonly used by the fertilizer industry in producinggranular fertilizers. The plaster of Paris, pesticidal powder or dustconcentrate and the other desired supplements, such as, clay or woodflour, are added to a premixer wherein these various materials areblended. From the premixer, the dry mixture is metered into a wetrotating granulator wherein metered water is introduced to the drymixture. In the granulator, the dry material is formed into wet balls ofabout inch in diameter, which are then passed to a rotary dryeroperating at about 100 C. When the granulated material is dry, it iscooled and passed to a crusher and then screened to obtain thegranulated particles of the desired size. The oversized particles arereturned to the crusher While the undersized particles are returned tthe wet granulator.

In order that those skilled in the art may better understand thecomposition of the present invention and the method in which it may beused, the following specific examples are given:

EXAMPLE 1 A mixture is made containing 79 parts by weight plaster ofParis and 8 parts by weight Natrin 80-S (sodium 2,4,5-trichlorophenoxyethyl sulphate). To this mixture is added 30 parts byweight water with constant stirring until the mixture forms wet balls ofabout /s inch in diameter. These wet balls are dried at C., crushed, andscreened, to obtain a granular mix which will pass through a screenhaving 20 openings per linear inch but will be retained on a screenwhich has 40 openings per linear inch. These granules are found to behard and do not disintegrate in water, but allow the Water-solublepesticide to be leached out. The finished granules are found to contain8% by weight of the pesticide material (N atrin 80-S).

EXAMPLE 2 A dry mix is made containing 69 parts by weight plaster ofParis and 20 parts by weight 50% wettable powder of3,4-dichlorotetrahydrothiophene 1,1-dioxide. To this dry mix is added 30parts by weight water with constant stirring until balling in themixture occurs. The mixture is dried at 100 0, ground and screened andthe granules collected which pass through a screen having 20 openingsper linear inch but are retained on a screen having 40 openings perlinear inch. These granules are found to be hard and do not disintegratein water. The final mixture is found to contain by weight of thepesticide.

EXAMPLE 3 Pesticidal granules are formed as in Example 2, with theexception that 3,3,4,4-tetrachlorotetrahydrothiophene 1,1-dioxide isused as the pesticidal agent. The granules collected are those whichpass through a screen having 30 openings per linear inch, but which areretained on a screen having 60 openings per linear inch. The granulesare found. to be hard and do not disintegrate in water and contain 10%by weight of the pesticidal material.

EXAMPLE 4 A dry mix is made containing 69 parts by Weight plaster ofParis and parts by weight 50% wettable powder of DDT. To this mixture isadded 35 parts by weight water with constant stirring until balling ofthe mixture is produced. The mixture is dried at 100 C., cooled, crushedand screened. The granules collected are those which pass through ascreen having openings per linear inch but are retained on a screenhaving 60 openin s per linear inch. These granules are found to be hardand do not disintegrate in water and contain 10% by weight of thepesticide material.

EXAMPLE 5 A dry mix is made which contains 5 parts by weight 2,44) acid,16 parts by weight attaclay and 68 parts by Weight plaster of Paris. Tothis mixture is added with constant stirring parts by weight of Wateruntil balling is produced in the mixture. The Wet mix is dried at 200 F,ground, screened, and the particles which pass through a screen having20 openings per linear inch and are retained on a screen having openingsper linear inch are collected. These granules are found to be hard butdo disintegrate slowly in water and contain 4% by weight of thepesticidal materials.

EXAMPLE 6 A pesticidal granule composition is made in the same manner asin Example 5, with the exception that 4 parts by weight 2,4,5-T are usedas the pesticidal material. As in Example 5, the granules collected arethose which pass through a screen having 20 openings per linear inch andare retained on a screen having 40 openings per linear inch. Thesegranules are found to be hard but do disintegrate slowly in water andcontain 4% by weight of the pesticidal agent.

EXAMPLE 7 A dry mix is made containing 76 parts by weight plaster ofParis, 2 parts by weight dust concentrate ofdimethyl-2,3,5,6-tetrachlorotercphthalate and 10 parts by weightbentonite. To this dry mix is added 40 parts by weight water withconstant stirring until balling in the mixture is produced. The moistmixture is dried at 100 (3., ground, screened and the granules whichpass through a screen having 20 openings per linear inch and areretained on a screen having 40 openings per linear inch are collected.These granules are found to be hard, disintegrate slcwly in water andcontain 1% by weight of the pesticidal material.

EXAMPLE 8 A dry mix is made which contains 69 parts by weight plaster ofParis, 10 parts by weight 50% wettable powder ofdimethyl-2,3,5,6-tetrachloroterephthalate, 5 parts by weight attaclayand 5 parts by Weight Wheat flour. To this mixture is added 35 parts byweight Water with constant stirring until the mixture begins to ball.The moist mixture is dried at 100 0, ground, screened and the granuleswhich pass through a screen having 30 openings per linear inch and areretained on a screen having 60 openings per linear inch are collected.These granules are found to be hard, distingrate slowly in water andcontain 5% by weight of the pesticidal material.

EXAMPLE 9 A dry mix is made which contains 30 parts by weight plaster ofParis, 3 parts by weight 50% wettable powder ofdimethyl-2,3,5,6-tetrachloroterephthalate, 40 parts by Weight Wyomingbentonite and 21.69 parts by weight agricultural gypsum. To this mixtureis added 35 parts by weight water with constant stirring untilpelletizing of the mixture takes place. The moist pellets are dried at100 C. and screened, and the pellets which pass through a screen having30 openings per linear inch and are retained on a screen having 60openings per linear inch are collected. These pellets are found to behard but disintegrate rapidly in water and contain 1.5% by Weight of thepesticidal material.

EXAMPLE 10 A granular composition is made as in Example 9 with theexception that 10 parts by Weight of the pesticidal material,dimethyl-2,3,5,6-tetrachloroterephthalate, and 14.8 parts by Weight ofthe agricultural gypsum are used. The granules thus formed are found tobe hard, but disintegrate rapidly in water and contain 5% by weight ofthe pesticidal material.

EXAMPLE 11 A granular composition is made as in Example 9 with theexception that 19.7 parts by weight of the pesticidal material, dimethyl2,3,5,6-tetrachloroterephthalate, and 5.1 parts by weight ofagricultural gypsum are used. The granules thus produced are found to behard, disintegrate rapidly in water and contain 10% by weight of thepesticidial material.

EXAMPLE 12 A dry mix is made which contains 83.5 parts by weight plasterof Paris and 3 parts by Weight 50% wettable powder ofdimethyl-2,3,5,G-tetrachloroterephthalate. To this mixture is added 36.7parts by weight of water with constant stirring until pelletizing of themixture takes place. The moist pellets are then dried at 100 C.,screened and the pellets which pass through a screen having 30 openingsper linear inch and are retained on a screen having 60 openings perlinear inch are collected. These pellets are found to be hard, undergosubstantially no disintegration in Water and contain 1.5% by weight ofthe pesticidal material.

EXAMPLE 13 To show the biological activity of the granule pesticides ofthe present invention, 97.6 parts by weight plaster of Paris and 2.4parts by Weight Natrin -5 (sodium 2,4,5- trichlorophenoxyethyl sulphate)are mixed together. To this dry mix is added 30 parts by weight waterwith constant stirring until balling of the mixture is produced. Theballed mixture is dried at C., screened, crushed and the particles whichpass through a screen having 20 openings per linear inch and areretained on a screen having 40 openings per linear inch are collected.These granules are applied to test plots containing tomatoes prior tothe emergence of the broadleaf weeds and grasses, at the rate 7 of 3 to6 pounds per acre. After a period of three weeks, the test plots areevaluated to determine the effectiveness of the granular formulation ofNatrin 80-5 with regard to broadleaf weed control, grass control andphytotoxic effect on tomatoes.

EXAMPLE 14 To test plots, similar to those in Example 13, a liquidsolution of Natrin 80-5 is applied, also at the rate of 3 and 6 poundsactive ingredients per acre. After a period of three weeks, the testplots are evaluted to determine the effectiveness of the liquidformulations of the Natrin 80-8 with regard to broadleaf Weed control,grass control and the phytotoxic effect on the tomatoes.

In the evaluations of Examples 13 and 14, the following indexes areused. Broadleaf control:

None 1Less than 2-Scattered 20 to 100 3Two or more areas of goodgermination 4-Heavy germination over 60% of plot 5Heavy germination overentire plot Grasses:

O-None 1Less than 50 2-Good germination in scattered areas 3-Goodgermination over wide area 4Heavy germination over 60% of plot 5Heavygermination over entire plot Phytotoxic response of tomatoes:

O--None 1-S1ight injury to less than 50% of plants 2Slight injury andarrested growth of all plants 3-Marked injury of to less than 50% of theplants 4-Marked injury to more than 50% of the plants 5Severe injury tomore than 75% of the plants Using these indexes, the following resultsare obtained:

Table I For Examples 13 and 14 Weeds Application Rate of ActiveMaterial, Formulation Tomatoes Pounds/Acre Br0ad- Grasses leafGranular 1. 75 2. 00 0 3 {Solution 1. 50 1. 75 .75 {Granular .25 75 1.50 6 Solution .50 1. 4. 00 Check 4. 75 4. 25 0 Table II For Examples 13and 14 Percentage of Treated Percent Application Rate Plants age of ofActive Ma- Live terial Pounds/ Formulation Plants Acre In- Dead to BearDead jured or In- Fruit,

jurcd From these results, it is seen that at an application rate of 3pounds per acre, nearly 10% more of the tomato plants treated with thegranular formulation bore fruit than those treated with the solutionformulation. Even more striking, is the fact that 40% more of the plantswhich were treated at the rate of 6 pounds per acre of the granularformulation bore fruit than those treated with the liquid formulation at6 pounds/ acre. It is, thus, obvious, from these tables, that thegranular formulation of the present invention gives marked advantages asto biological activity and selectivity over a solution formulation.

While the method of the present invention has been described withprimary references to the preparation of pesticidal compositions, it isto be appreciated that other biologically active materials, such as forexample, plant growth regulants which are absorbed through the rootsystems of the plants, can also be so prepared.

While there has been described an embodiment of the invention, theproducts and methods described are not intended to be understood aslimiting the scope of the invention, as it is realized that changes andalterations therewithin are possible and that it is further intendedthat each element recited in any of the following claims is to beunderstood as referring to all equivalent elements for accomplishingsubstantially the same results in substantially the same or equivalentmanner, it being intended to cover the invention broadly in whateverform its principle may be utilized.

What is claimed is:

1. A method of making a biologically active composition comprisingforming a dry mixture comprising a dehydrated calcium sulfate and abiologically active material, slowly adding water to said dry mixture,mixing said dry mixture and water so as to form pellets comprised ofcalcium'sulfate dihydrate and having the biologically active materialintimately and substantially uniformly dispersed therethrough; the totalamount of water added to said dry mixture being sufiicient only to formthe dihydrate of the calcium sulfate and effect pelletizing of saidmixture, said total amount of water being from about 2 to 6 times theamount required to form the dihydrate.

2. The method as claimed in claim 1 wherein the dehydrated calciumsulphate is plaster of Paris.

3. A method of making a pesticidal composition comprising forming a drymixture comprising essentially a dehydrated calcium sulfate and apesticide, slowly adding water to said dry mixture, mixing said dryingredients and water so as to effect the formation of pelletscomprising the dihydrate of calcium sulfate and having intimately andsubstantially uniformly dispersed therein the pesticidal material, thetotal amount of water added to said dry mixture being sufiicient only toform the dihydrate of said calcium sulfate and effect pelletizing of themixture, said total amount of water being from about 2 to 6 times theamount required to form the dihydrate.

4. The method as claimed in claim 3 wherein the dehydrated calciumsulphate is plaster of Paris.

5. A method of making a pesticidal composition comprising forming a drymixture containing 25 to 98 parts by weight of plaster-of-Paris, 2 to 40parts by weight of a pesticide and 0 to 60 parts by weight of clay,slowly adding Water to said dry mixture, mixing the dry mixture andwater to effect the formation of pellets comprising calcium sulfatedihydrate and having intimately and substantially uniformly dispersedtherein said pesticide and drying the thus formed pellets, the totalamount of water added to said mixture being sufficient only to convertthe plaster-of-Paris to calcium sulfate dihydrate and effect pelletizingof the mixture, said total amount of water being from about 2 to 6 timesthe amount required to convert the plaster-of-Paris to calcium sulfatedihydrate.

6. The method as claimed in claim 5 wherein the pellets formed are of aparticle size which will pass through a screen having 10 openings perlinear inch but which will 2,242,639 be retained on a screen having 80openings per linear inch. 2,592,540 7. The method as claimed in claim 5wherein a portion 2,809,469

of the clay is replaced with a swelling agent.

References Cited in the file of this patent UNITED STATES PATENTS1,973,473 Edwards Sept. 11, 1934 10 Barton May 20, 1941 Cassil et a1.Apr. 15, 1952 Hartley Oct. 15, 1957 FOREIGN PATENTS Australia Mar. 27,1958

1. A METHOD OF MAKING A BIOLOGICALLY ACTIVE COMPOSITION COMPRISINGFORMING A DRY MIXTURE COMPRISING A DEHYDRATED CALCIUM SULFATE AND ABIOLOGICALLY ACTIVE MATERIAL, SLOWLY ADDING WATER TO SAID DRY MIXTURE,MIXING SAID DRY MIXTURE AND WATER SO AS TO FORM PELLETS COMPRISED OFCALCIUM SULFATE DIHYDRATE AND HAVING THE BIOLOGICALLY ACTIVE MATERIALINTIMATELY AND SUBSTANTIALLY UNIFORMLY DISPERSED THERETHROUGH, THE TOTALAMOUNT OF WATER ADDED TO SAID DRY MIXTURE BEING SUFFICIENT ONLY TO FORMTHE DIHYDRATE OF THE CALCIUM SULFATE AND EFFECT PELLETIZING OF SAIDMIXTURE, SAID TOTAL AMOUNT OF WATER BEING FROM ABOUT 2 TO 6 TIMES THEAMOUNT REQUIRED TO FORM THE DIHYDRATE.